Ignition module maybe

[exceliom]

So.
I have this problem.
The spark is so weak that it sometimes won't even light the timing light.
Would I be right to assume that it could possibly be the Lucas box thing?
A long time ago there was a bit on here about replacing it with an alternative.
I'm open to all sorts of alternatives . Did a forum search but unfortunately can't find the thread.
I'll appreciate any help.

[Marten]

So.
I have this problem.
The spark is so weak that it sometimes won't even light the timing light.
Would I be right to assume that it could possibly be the Lucas box thing?
A long time ago there was a bit on here about replacing it with an alternative.
I'm open to all sorts of alternatives . Did a forum search but unfortunately can't find the thread.
I'll appreciate any help.

Could be, but.....Your timing light is triggered by a high voltage surge in the ignition lead. If the leads are shorted to ground, or the distributor cap has failed, or the rotor has burned through , or if the coil is bad or if t is not getting proper voltage your Lucas unit won't be the one to blame.
I'd start with connecting a headlight bulb between coil power and ground, and see if you retain decent power when cranking

[Hawaiis0]

The AB14 gets a lot of stick for failing. So far all our tests have never found a failed unit.

The innards of the unit are a standard GM part and can be got of ebay for peanuts. Easy to swap too.

I'll find the number later.

i have a test lucas module . Any chance you'll be at the NEC next month?

Stu

edit see viewtopic.php?f=27&t=9478&p=71233&hilit ... ace#p71233

[Hawaiis0]

Have you got a good battery? Crank with your headlights on is a quick test

[rbgosling]

Yeah, I'd agree with Marten - while the AB14 is not impossible, it's the last thing I'd check after I'd already ruled out:

• HT leads
• Distributor cap
• Rotor arm
• Coil
• Spark plugs

All of these other things are more likely, and easier to test, and cheaper to replace.

Being a box of electronics, I'd have expected the AB14 to either work, or not work. Being a bit feeble isn't really electronic's thing. But this is a generic comment, so if someone has experienced a feeble spark and diagnosed the AB14 as the cause, I'll accept that verdict!

One last comment - for months after I rebuilt my engine it would frequently not start - clearly an ignition problem as, when it did start, it would run perfectly. And messing with the distributor usually got it going, eventually. Finally diagnosed as me failing to install one tiny washer in the distributor, which meant that one component could move a bit on its shaft when it should be tightened down, and thus wasn't always earthing reliably. But, again, that was an on/off fault, not working-but-feeble.

[exceliom]

Things that are new.
Coil
Leads
Distributor cap
Rotor arm
Carb rebuild (twice)
Carb balance
mixture set
Timing, a lot.
So the symptoms are .
Generally starts very easily but won't pick up on the revs. Then stops and won't restart for days.
The battery is very good normally connected to a jumper pack to make sure.
the cranking voltage at the coil is 9.8v and have given that a hot wire straight from the booster pack ( quality unit).
In my opinion, it seems to be drowning out the spark.
rev limiter has been disconnected.
I'm loosing my mind with this now.

[richardw]

Quick thought - is the fuel pump good? Fuel filter? Your symptoms sound more fuelling than ignition related to me, especially as it won’t pick up revs, but what do I know?

The other area to check is the vacuum system. Leaks there could cause this type of problem.

Good luck with this,

Richard

[Marten]

Things that are new.
Coil
Leads
Distributor cap
Rotor arm
Carb rebuild (twice)
Carb balance
mixture set
Timing, a lot.
So the symptoms are .
Generally starts very easily but won't pick up on the revs. Then stops and won't restart for days.
The battery is very good normally connected to a jumper pack to make sure.
the cranking voltage at the coil is 9.8v and have given that a hot wire straight from the booster pack ( quality unit).
In my opinion, it seems to be drowning out the spark.
rev limiter has been disconnected.
I'm loosing my mind with this now.

My first guesses (from miles away without knowing what it sounds like) is that it drowns in fuel and won't restart untill that's gone. And I can't connect 'Carb balance' , 'mixture set' and 'Generally starts very easily but won't pick up on the revs. Then stops and won't restart for days' .

Given alll the new bits:
check that the coil isn't in backwards (#15 should be the 12V)
check your firing order, eg does the distributor rotates the way you think

[Alan_M]

Have you removed the plugs after it starts and then stops- are they dry, wet, sooted up etc

Was it a riveted rotor arm that was fitted?

[Zaphod]

My first guesses (from miles away without knowing what it sounds like) is that it drowns in fuel and won't restart untill that's gone. And I can't connect 'Carb balance' , 'mixture set' and 'Generally starts very easily but won't pick up on the revs. Then stops and won't restart for days' .

Given alll the new bits:
check that the coil isn't in backwards (#15 should be the 12V)
check your firing order, eg does the distributor rotates the way you think

That sounds nastily like the issue a lot of nicasil 4.0 and 3.2 jag V8s had. They would start and if shutdown before warm would not start for days unless you dropped a small amount of oil in the cylinders, then they would start immediately. The cure was either live with it or new liners/block!

[bash]

When I put the V8 in I had a wierd running issue too. There were two issues with mine that might be worth checking on yours. I firstly found that the ignition switch contacts were poor restricting power, but the main reason was that the king lead for the coil had far too much internal resistance and it was restricting its power output to the distributor.
I was on the IOM 2 weeks ago, I could have visited and shared the headache.

Bash

Edit, Another thought, I know you changed the distributor cap, but is the carbon centre bush contacting the rotor arm correctly?

[rbgosling]

My first guesses (from miles away without knowing what it sounds like) is that it drowns in fuel and won't restart untill that's gone. And I can't connect 'Carb balance' , 'mixture set' and 'Generally starts very easily but won't pick up on the revs. Then stops and won't restart for days' .

Given alll the new bits:
check that the coil isn't in backwards (#15 should be the 12V)
check your firing order, eg does the distributor rotates the way you think

That sounds nastily like the issue a lot of nicasil 4.0 and 3.2 jag V8s had. They would start and if shutdown before warm would not start for days unless you dropped a small amount of oil in the cylinders, then they would start immediately. The cure was either live with it or new liners/block!

Drifting slightly off-topic here, but I'm very curious about the mechanism of this problem. I struggle to see how the liner would affect engine starting. The only thing that occurs to me would be somehow the piston getting stuck in the liner so the engine won't even turn over?

[Marten]

Drifting slightly off-topic here, but I'm very curious about the mechanism of this problem. I struggle to see how the liner would affect engine starting. The only thing that occurs to me would be somehow the piston getting stuck in the liner so the engine won't even turn over?

Or the opposite? Maybe the engine cranks too fast with loss of compression, and runs of the map with all the settings used for starting

[Lotus-e-Clan]

Drifting slightly off-topic here, but I'm very curious about the mechanism of this problem. I struggle to see how the liner would affect engine starting. The only thing that occurs to me would be somehow the piston getting stuck in the liner so the engine won't even turn over?

Or the opposite? Maybe the engine cranks too fast with loss of compression, and runs of the map with all the settings used for starting

Sounds plausible, but what's the cause of it stopping once warm?

We know that our SE engines with Nikasil liners and forged pistons run better /quieter once warmed up. I seem to recall that one of the causes of issues with Nikasil liners is running them normally at too low a temperature. e.g. It's not good to run them with a low 75C stat, better to run them normally at 82C (or a bit higher).

My next door neighbour has a XKR Jag which sounds horrendous on cold starting (piston slap) but quietens after a minute or two idling and sounds sweet when fully warmed.

[bash]

I thought nikasil issues disappeared with high sulphur petrol and was no longer an issue. Am I wrong ?
Bash